1. Field of the Invention
This invention relates generally to adhesive articles and, more specifically, to adhesive articles that are useful for protecting motor vehicles during manufacture, transport and storage.
2. Description of the Related Art
Motor vehicles are painted early in the manufacturing process. Once painted, the body of the vehicle moves along an automated assembly line so that other parts can be added. During this process the vehicle may be inadvertently hit, nicked, dinged, etc. by assembly line workers, nearby equipment, tools, etc. Depending on the severity of the damage, it may be necessary to repaint part of the vehicle, which is an expensive and time consuming process. Once manufactured, the vehicles are shipped by railroad, truck or ship to distribution centers, and eventually to dealers who will sell the vehicles. While in transit, the vehicles may become damaged or discolored due to flying road gravel, soot, metal particulates, exhaust gases, harsh sunlight, leaking fluids (for example, from adjacent vehicles or the carrier), acid rain, bird dung, numerous chemicals, etc. Severe damage may require that the vehicles be repainted. Vehicles may sit on open-air dealer lots for several weeks or more before they are sold. During this time they can be damaged by many of the hazards that arise during shipping as well as by incidental contact from salespeople and potential buyers. This could result in part of the vehicle having to be repainted.
One way to safeguard motor vehicles during manufacture, transport and storage is to use a protective adhesive article such as a protective adhesive sheet or adhesive tape (i.e., a backing with an adhesive on it). Adhesive articles useful for protecting motor vehicles should have certain attributes. For example, they should not leave an imprinted pattern on the painted surface of the motor vehicle. Variations in raw materials and manufacturing processes may cause the paints used on some vehicles to cure more slowly than the paints used on other vehicles. Partially cured paints may be "softer" than fully cured paints. Also some manufacturers prefer to use "softer" paints. In addition, when the vehicles are being shipped, temperatures may become as high as about 80.degree. C., which can cause some paints to soften. Consequently, the adhesive used in the protective film should be softer than the paint that it touches, since a less flowable adhesive could leave an undesirable imprinted pattern on the painted surface.
The adhesive should provide good adhesion to the painted vehicle so that the protective article does not come off during use. However, it should not be difficult to remove the article when it is no longer needed. The protective article should also remove cleanly without leaving traces of adhesive residue on the painted vehicle. In addition, it is desirable that the protective article be recyclable. Increasing concern for the environment has created a demand for waste and packaging that can be recycled.
Several methods have been developed to protect motor vehicles during manufacture, transport and storage. For example, water soluble or dispersible compositions have been sprayed as temporary coatings which can later be removed with water or alkali. See for example, U.S. Pat. No. 4,525,501 (Norman et al), U.S. Pat. No. 3,642,567 (Rogers, Jr.), and U.S. Pat. No. 5,006,578 (Masuda et al). Another method involves spraying a composition on the surface to be protected, drying or curing the composition, and subsequently removing the resulting film by stripping or peeling. For examples, see British Patent Publication Nos. 2,191,717 and 2,253,401 (each to Gramos Chemical).
As suggested before, another method of protection uses a tape or sheet which includes a pressure sensitive adhesive (PSA) on a backing or support. The tape or sheet is removed from the motor vehicle when it is no longer needed. U.S. Pat. No. 5,286,781 (Gotoh et al) describes a tape or sheet having a PSA containing a block copolymer, a tackifying resin, and a polyolefin. European Patent Publication No. 519,278 (Matsui et al) describes a protective sheet that uses a rubber based PSA having a dynamic modulus of from 2.times.10.sup.5 to 7.times.10.sup.6 dynes/cm.sup.2 at 60.degree. C. Japanese Kokai Patent Application No. Hei 6[1994]-128538 (Matsui et al) describes a very similar protective sheet that is supplemented by the addition of an anti-static agent. Japanese Kokai Patent Application No. Hei 6[1994]-128540 (Tsuchibashi et al) discusses a protective film having an adhesive layer containing a polyisobutylene or butyl rubber and a primer for bonding the adhesive to a colored olefin-type support film. Japanese Kokai Patent Application No. Hei 5[1993]-98223 (Kawabata et al) discusses a surface protection film having an adhesive layer consisting of a block copolymer, a tackifier resin, and an ethylene .alpha.-olefin copolymer and/or propylene .alpha.-olefin copolymer on one side of a polyolefin type base film.
However, there still remains a need for improved protective adhesive articles that will not imprint the painted surface of a motor vehicle, that have good adhesion, that can be cleanly and easily removed when no longer needed, and that can be recycled.